1. Technical Field
This invention generally relates to welding machines. More particularly, the invention relates to welding machines that are used to weld flexible sheet materials together. Specifically, the invention relates to a fabric welding machine that includes an expandable top beam for supporting a welding head in an appropriate position over an expandable vacuum track assembly, where the vacuum track assembly utilizes suction to retain the fabrics to be welded in an immobilized position beneath the welding head.
2. Background Information
Heat welding has long been used to join waterproof sheet materials together to manufacture a variety of products such as tents, tarpaulins, liners for pools and landfills, awnings and others. During the manufacturing process, two pieces of sheet material are overlapped and a combination of heat and pressure is applied to the overlapped region to weld the materials together and create a seam. This procedure permits longer pieces of the waterproof sheet materials to be produced so that the end product can be manufactured out of the same.
Various techniques have been developed to join sheet materials of this nature together. These include hot air welding, hot wedge welding and impulse welding. In hot air welding a nozzle is positioned so as to blow heated air between the two layers of sheet material. Typically, for a thermoplastic sheet material, the temperatures involved range anywhere from 200 F to 1,350 F (90 C to 750 C). Once the heat has been introduced between the layers, a roller passes over the same, applying a preset level of pressure to the layers. The combination of the heat and pressure joins the materials together. Hot air welding requires precise temperatures and pressure to be applied to the sheet materials and also requires that the process be done in a timely fashion in order to prevent cooling of the sheet materials before the roller passes over the same. If the temperature or pressure is off, the weld will not be complete and the materials may separate from each other.
Hot wedge welding is fairly similar to hot air welding, with the exception that instead of a nozzle being used to introduce heat into the system, a heated wedge is used. The wedge is positioned so that the fabric layers are pulled over the wedge immediately before they are contacted by the rollers. Wedges are typically heated to a temperature of between 200 F and 920 F (90 C and 490 C). Once again, the temperature, pressure and time have to be closely monitored in order to create a good seam.
Some of the problems surrounding welding of a first and a second fabric panel together by any of the above mechanisms are the need to apply heat and pressure in a consistent zone on the fabric panels and the need to keep the panels immobilized during the application of heat and pressure thereto. If either of the panels move, or the heat or pressure is not applied in a consistent area on the panels, the quality of the seam so produced will suffer.
There is therefore a need in the art for an improved fabric welding machine that more consistently applies heat and pressure to a region of fabric panels that are to be welded together, and provides mechanisms for immobilizing those fabric panels as they are welded.